1. Field
The present disclosure relates to electronic circuitry and, more specifically but not exclusively, to operating circuitry during over-voltage conditions.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
FIG. 1 is a simplified block diagram of a portion of a prior-art integrated circuit (IC) 100. As shown in FIG. 1, integrated circuit 100 provides two exemplary circuit functions: (i) analog signal processing implemented by an analog amplifier 104 and a signal processing circuit 106 and (ii) analog signal measurement for out-of-range voltage detection that triggers an alarm implemented by comparator 108 and flip-flop 110, all of which are powered by a local (i.e., on-chip) power supply consisting of a positive power supply voltage VDD and a negative power supply voltage (i.e., ground reference voltage) GND. The two exemplary circuit functions are driven by a differential analog input signal consisting of a positive input signal Vplus and a negative input signal Vminus that are applied to two IC input nodes, which can also be respectively referred to by the labels Vplus and Vminus. Application of the input signals Vplus and Vminus, as well as a reference signal Vtrip, to the two exemplary circuit functions is controlled by a set of clock-driven switches 102 driven by clock signal CLK. In other words, the two exemplary circuit functions are gated by the clocked switches 102. The rest of the details of these two exemplary circuit functions are not important for the present disclosure.
In many applications, the voltage levels of the input signals Vplus and Vminus stay within the supply voltage range for the IC. That is, the positive input signal voltage Vplus is always less than or equal to the positive supply voltage VDD, and the negative input signal voltage Vminus is always greater than or equal to the negative supply voltage GND. There are, however, applications that require handling voltages in excess of the IC supply voltage range. Handling voltages which exceed the IC supply voltage range usually require some special circuit techniques unless the signals can simply be divided down using a resistor divider to within the IC supply voltage range. Where dividers are not appropriate, e.g., when the input voltages can vary significantly and dynamically, such as from GND up to twice or more of the IC supply voltage VDD, circuit functions such as precision analog measurement present a challenge.